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Echoless light could help send signals through walls and skin

IT’S a call with no response. A new way of creating waves that don’t echo promises to improve everything from your Wi-Fi signal to medical imaging.

As a wave travels it can become scattered, like an echo. This is a problem in telecommunications&colon; if you send digital signals down a very long optical fibre, the pulses stretch out and 1s start to blend into 0s.

Now Joel Carpenter at the University of Queensland in Brisbane, Australia, and his colleagues have demonstrated a workaround.

The team started with a 100-metre-long fibre-optic cable and shone light through it. As expected, the light emerging at the other end had become distorted.

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They measured the exact degree of distortion and how the profile of the pulse changed on its journey through the fibre. This shape determines what path photons take down the fibre, and how they interfere with each other, Carpenter says.

Finally, they created a light pulse with the exact cross-section needed to counteract the distortion and emerge from the fibre intact – and found that it did just that (Nature Photonics, DOI&colon; 10.1038/nphoton.2015.188).

“Even though it might get scattered as it goes through, it will all semi-magically show up at exactly the same time at the other end,” says Carpenter.

The scheme could have important applications, for instance, allowing medical imaging devices to peer deeper into tissue than is now possible.

This article appeared in print under the headline “Light without an echo could peer deeper into our bodies”